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Sumathi T.,BNM Institute of Technology | Sundaram P.S.,TUV Rheinland India Pvt. Ltd. | Chandramohan G.,AVVM Sri Pushpam College
Arabian Journal of Chemistry | Year: 2011

The kinetics and mechanism of Ag(I)-catalyzed oxidation of l-alanine by cerium (IV) in sulfuric acid media have been investigated by titrimetric technique of redox in the temperature range of 298-313K. It is found that the reaction is of first order with respect to Ce(IV) and l-alanine, and it is of a positive fractional order with respect to Ag(I). It is found that the pseudo first order ([l-alanine]≫[Ce(IV)]≫[Ag(I)]) rate constant k' increases with the increase of [H+]. The major oxidation product of alanine has been identified as acetaldehyde by an 1H NMR and IR spectroscopy. Under the experimental conditions, the kinetically active species has been found to be Ce4+. Under nitrogen atmosphere, the reaction system can initiate the polymerization of acrylonitrile, indicating generation of free radicals. On the basis of the experimental results, a suitable mechanism has been proposed. The rate constants of the rate-determining step together with the activation parameters were evaluated. © 2010. Source


Sumathi T.,BNM Institute of Technology | Shanmugasundaram P.,TUV Rheinland India Pvt. Ltd. | Chandramohan G.,AVVM Sri Pushpam College
Asian Journal of Chemistry | Year: 2012

The kinetics of the oxidation of silver(I) catalyzed oxidation of L-tyrosine, N-acetyl L-tyrosine (L-tyr & N-A-tyr) by Ce(IV) in sulfuric acid medium at a constant ionic strength of 0.1 mol dm-3 was studied spectrophotometrically (stopped flow fluorimetry). The reaction between L-tyrosine, N-acetyl L-tyrosine and Ce(IV) in sulfuric acid medium in presence of [Ag(I)] exhibits 1:2 stoichiometry. The reaction was first order with respect to L-tyrosine, N-acetyl L-tyrosine, inverse order with respect to Ce(IV) and a positive fractional order with respect to Ag(I). Intervention of free radicals was observed in the reaction. The oxidation reaction in sulfuric acid medium has been shown to proceed via a Ag(I)-L-tyr and N-A-tyr complex, which reacts with Ce(IV) to decompose in a rate determining step followed by other fast steps to give the products. The main products were identified by LC-ESI-MS and IR spectra. Probable mechanism is proposed and discussed. The activation parameters with respect to the slow step of the mechanism were computed and discussed and thermodynamic quantities were also calculated. The active species of oxidant has been identified as Ce(SO 4) 2. Source


Sumathi T.,BNM Institute of Technology | Shanmugasundaram P.,TUV Rheinland India Pvt. Ltd. | Chandramohan G.,AVVM Sri Pushpam College
Asian Journal of Chemistry | Year: 2011

The kinetics of the Ag(I) catalyzed oxidation of L-leucine by cerium(IV) in H2SO4 medium has been investigated at 323 K. The reaction was first order with respect to L-leucine, inverse order with respect to Ce(IV) and a positive fractional order with respect to Ag(I). Increase in [H +] decreased the reaction rate. The added SO4 2 and HSO4 - decreased the rate of the reaction. Under the experimental conditions, the kinetically active species of cerium has been found to be Ce(SO4)2. The major oxidation product of L-leucine has been identified as pentanaldehyde which is confirmed by the IR spectrum. Effects of bivalent and trivalent catalyst have also been studied. Under nitrogen atmosphere, the reaction system can initiate the polymerization of acrylonitrile, indicating the generation of free radicals. A suitable mechanism involving the formation of an intermediate complex with silver catalyst has been proposed. Source


Sumathi T.,BNM Institute of Technology | Shanmugasundaram P.,TUV Rheinland India Pvt. Ltd. | Chandramohan G.,P.A. College
Journal of Saudi Chemical Society | Year: 2013

The kinetics and mechanism of Ag(I) catalyzed oxidation of l-Serine by cerium(IV) in sulfuric acid media has been investigated by titrimetric technique of redox in the temperature range of 293-308K. The reaction was first order with respect to serine, inverse order with respect to Ce(IV) and a positive fractional order with respect to Ag(I). Increase in [H+] decreased the reaction rate. The added SO42- decreased the rate of the reaction. Under the experimental conditions, the kinetically active species of cerium has been found to be Ce(SO4)2. The major oxidation product of serine has been identified as glycoldehyde which is confirmed by the IR spectrum of a corresponding hydrazone. Under nitrogen atmosphere, the reaction system can initiate the polymerization of acrylonitrile, indicating the generation of free radicals. On the basis of the experimental results, a suitable mechanism has been proposed. The rate constants of the rate determining step together with the activation parameters were evaluated. © 2011. Source


Herrmann W.,TUV Rheinland Energie und Umwelt GmbH | Schweiger M.,TUV Rheinland Energie und Umwelt GmbH | Tamizhmani G.,TUV SUD | Shisler B.,TUV SUD | Kamalaksha Cs.,TUV Rheinland India Pvt. Ltd.
2015 IEEE 42nd Photovoltaic Specialist Conference, PVSC 2015 | Year: 2015

During long-term operation of photovoltaic (PV) power plants soiling of PV module surface can cause significant energy yield losses. These are dependent on the site characteristics such as climatic conditions or surrounding environment, and also on the glazing characteristics of the PV module. This paper presents the results of an experimental study on annual soiling losses measured at two locations: a) Tempe (Arizona) with hot and dry climate, b) Chennai (India) with tropical climate. Soiling effects were studied by means of two mini-modules, of which one has been regularly cleaned whereas the other was exposed to natural soiling. For the first year of operation our results show 3.7% annual soiling losses for Tempe and 2.3% for Chennai. The contribution of angular losses caused by the change of the angular characteristic of the glass surface is approx. 22% for the Tempe test site. Comparative study of the soiling behavior of 3 types of PV glazing (standard glass, standard glass with antireflective coating, deeply textured glass) showed that AR coating is comparable to non-coated glass. For deeply textured glass we observed 7% higher annual soiling loss at Tempe test site. © 2015 IEEE. Source

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